Reciprocating piston internal combustion engines include one or more pistons that are reciprocally disposed within corresponding combustion cylinders. The pistons are interconnected with each other through the use of a rotatable crankshaft. Rotation of the crankshaft causes each piston to reciprocate within its corresponding combustion cylinder. Typically, each piston is pivotally connected to one end of a connecting rod. The connecting rod includes an eye defining an eye bearing that receives a piston pin of the piston such that the connecting rod pivots through a relatively small pivoting angle about the piston pin during reciprocation. The other end of the connecting rod is also pivotally coupled to the crankshaft which also pivots through a relatively small angle. Lubrication of the moving and pivoting parts within an internal combustion engine is essential during operation, as the lubricant eases friction between moving/pivoting parts and aids in the removal of heat. The lubricant generally used is oil. One area where it is desired to provide lubrication in the internal combustion engine is the piston pin of a piston.
It is known to indirectly supply a lubricant such as oil to the piston pin by splashing the oil proximate the piston pin area. In one form, oil that is sprayed onto the piston undercrown area specifically for cooling the piston crown splashes onto the connecting rod eye of the connecting rod. Since the connecting rod eye is disposed about the piston pin, the oil wicks into the connecting rod eye bearing area defined between the piston pin and the connecting rod eye to provide lubrication. While the splash method does supply lubricant to the piston pin area, the amount of lubricant supplied to the piston pin by the splash method may not be satisfactory. Further, the splash method is a passive rather than an active or positive method of providing lubrication to the piston pin and thus is not preferable.
It is also known to supply lubricant to the piston pin via a bore drilled longitudinally through a corresponding connecting rod. The connecting rod bore is in fluid communication with a lubricant supply via the crankshaft. In this manner, pressurized lubricant may be provided to the piston pin such that this is a positive method of lubrication. However, the structural integrity of the connecting rod is compromised by the connecting rod bore itself. Alternatively, if the connecting rod is enlarged to compensate for the rod bore, thereby preserving the structural integrity of the connecting rod, weight and size for example, then become of particular concern. Thus, providing a connecting rod bore for supplying lubricant to the piston pin is not preferable. Additionally, this method is prone to unacceptable oil leakage from the bearing on the crankshaft.
The present invention is directed to overcoming one or more of the problems as set forth above.